PSLV-C25/Mars Orbiter Mission

PSLV-C25/Mars Orbiter Mission

MARS: The red planet

Mars is the only planet of our solar system that remarkably resembles our
Earth in many prominent respects. Thus, it is perhaps the best place to
search for past or present life outside the Earth. For this reason, Mars has
become the target of many unmanned spacecraft from Earth after the dawn
of space age in 1957.

Mars lies outside the Earth’s orbit and revolves round the Sun in an elliptical
orbit. Its orbital period is 687 days compared to the Earth’s 365 days. Mars
takes 24 hours and 39 minutes to spin around its own axis once, which is
strikingly similar to a ‘day’ on Earth. Besides, the axial tilt of Mars is about
25 deg, which is very similar to that of Earth and results in seasons which
are about twice as long as those on Earth.

For thousands of years, humans have observed Mars in the night sky as a
red dot of light moving slowly against the background of ‘fixed’ stars over a
period of weeks. Ancient Romans named it after their god of war because of
its red colour. But the orange red colour of the planet is due to the presence
of Iron oxide all over its surface. Mars has polar ice caps which consist of
solid carbon di oxide as well as water ice which expand and shrink with
seasons. Besides, seasonal appearance of dark patches on the surface of
Mars made humans to suspect the presence of vegetation on Mars.

Strong similarities between Earth and Mars, and, more importantly, optical
illusions during the 19th century telescopic observation of Mars, made
humans to suspect the presence of life, especially intelligent life, on Mars.
But, robotic spacecraft that have landed on the surface of Mars have not
shown any evidence of intelligent life and have not even conclusively
detected microbial life there. So, the exploration of Mars through orbiting
spacecraft as well as landers and rovers is continuing to seek answers to
some of the most fundamental and profound questions about planetary
evolution as well as origin and sustenance of life.

India’s Mars Orbiter Mission is the essential part of the current global effort
to understand Mars in greater detail. Today, that effort is mainly focused
towards finding out the suitability of Mars in the past to give raise to life and
sustain it as well as to search for life on Mars today. This is being
endeavoured through both direct and indirect search for Martian life.

Objectives
India’s Mars Orbiter Mission is more of a Technology Demonstration
Mission than a scientific mission.

Scientific Objectives of Mars Orbiter Mission:

Exploration of surface features, topography, morphology, minerology and
atmosphere of Mars through an orbiting spacecraft

The main technological objectives of Indian Mars Orbiter Mission are:

      Design and realisation of a Mars orbiter spacecraft capable of
       travelling towards Mars, getting into an orbit around that planet
       and conduct in-orbit observation of Mars
      Demonstration of the capability to perform deep space
       communication, navigation, mission planning and management
      Incorporation of Autonomous features in the spacecraft to handle
       contingency situations

Major Challenges
   Selection, qualification and incorporation of radiation hardened
    components in a spacecraft operating in deep space
   Design and realisation of a spacecraft capable of operating over a
    wide temperature range near the Earth as well as Mars
   Ensuring the restart and proper functioning of the Liquid Apogee
    Motor (LAM) of the spacecraft after a dormant period of 10 months
   Power management due to reduction in the electric power output of
    Solar Panels due to lower solar radiation and very low temperatures
    in Martian orbit
   Spacecraft communication management in deep space with the
    associated delay time
   Incorporation of spacecraft autonomy due to a communication delay
    time of up to 42 minutes
   Design, development, testing and qualification of navigation software
    to accurately send a spacecraft towards Mars and to place it into an
    orbit around it

The Launch Vehicle
The vehicle chosen for launching the 1340 kg Mars Orbiter spacecraft is
PSLV-XL, the most powerful version of India’s workhorse Polar Satellite
Launch Vehicle. This mission to launch Mars Orbiter Mission Spacecraft
using PSLV is designated as PSLV-C25 and this is PSLV’s twenty fifth
flight.
PSLV-C25 will be launched from the First Launch Pad at Satish Dhawan
Space Centre SHAR, Sriharikota. PSLV-C25 is the fifth flight of PSLV-XL
that carries longer and heavier strap-on motors compared to the standard
version of PSLV. It stands 44.4 metre tall (fifteen storeys high) and has a
lift-off weight of 320 tons.
The challenging PSLV-C25 mission is optimised for the launch of Mars
Orbiter spacecraft into a highly elliptical Earth orbit with a perigee (nearest
point to Earth) of 250 km and an apogee (farthest point to Earth) of
23,500 km with an inclination of 19.2 degree with respect to the equator. It
takes about 44 for PSLV-C25 to inject Mars Orbiter Mission spacecraft into
that orbit and 37 seconds later, the spacecraft gets separated from the
fourth stage of PSLV-C25.
Compared to all its earlier missions, PSLV-C25 is very different in one
respect since after the separation of its third stage, there will be a long
coasting phase of about 25 minutes before the ignition of the fourth stage.
This is done to ensure that the spacecraft later achieves minimum energy
transfer route from Earth to Mars. Thus, the first phase of Mars Orbiter
Mission spacecraft’s journey to Mars will be completed in about 44 minutes
after lift-off when the spacecraft starts orbiting the earth independently.
Since no existing ground station of ISRO Telemetry, Tracking and
Telecommand Network (ISTRAC) will have visibility to monitor the ignition
and performance of the fourth stage of PSLV-C25 as well as the subsequent
spacecraft separation, two ship borne terminals located in the Pacific Ocean
will be utilised for monitoring those critical events. This is the first time ship
borne ground station terminals are used to monitor an ISRO launch vehicle
mission.

PSLV-C25 STAGES AT A GLANCE

                            Stage 1      PSOM-XL       Stage 2       Stage 3      Stage 4

  Length (m)                   20           12           12.8          3.6          2.7

  Diameter (m)                 2.8           1            2.8           2           2.8

  Propellant                  Solid        Solid        Liquid        Solid        Liquid
                             (HTPB        (HTPB         (UH25        (HTPB        (MMH+
                             based)       based)        +N2O4)       based)       MON3)

  Propellant Mass (Ton)       138          12.2           42           7.6          2.5

  Peak Thrust (kN)            4800          719          799           247         7.3x2

  Burn Time (Sec)             103           50           148           112          525
         HTPB : Hydroxyl Terminated Poly Butadiene, UH25 : Unsymmetrical Dimethyl Hydrazine +
         25% Hydrazine Hydrate, N2O4 : Nitrogen Tetroxide, MMH : Mono Methyl Hydrazine,
         MON-3 : Mixed Oxides of Nitrogen

Flight Profile of PSLV-C25:
Events                                    Time (s)                   Local          Inertial
                                                                     Altitude       Velocity
                                                                     (km)           (m/s)

Mars Orbiter Mission Spacecraft 44 Min 17 sec                        383.39         9804.0
Separation

Fourth Stage Burn Out                     43 Min 40sec               342.51         9833.5

Fourth stage Ignition                     33 Min                     271.32         7642.0

Third Stage Separation                    9 Min 44 sec               194.87         7730.9

Third stage Ignition                      4 Min 26 sec               132.53         5378.94

Second Stage Separation                   4 Min 25 sec               132.31         5370.33

Heat Shield Separation                    3 Min 22 sec               113.17         3624.69

Second Stage ignition                     1 Min 53 sec               57.85          2387.16

First Stage Separation                    1 Min 53 sec               58.00          2388.0

Air Lit Strap-on Separation               1 Min 32 sec               39.70          2024.3

Ground Lit Strap-on Separation            1 Min 10 sec               23.50          34.5

Air Lit Strap-on Ignition                 25 sec                     2.67           612.0

Ground Lit strap-on Ignition              0.5 sec                    0.02           451.9

First stage Ignition                      0 sec                      0.02           451.9

The Journey
As the Mars Orbiter spacecraft circles the earth, by firing the spacecraft’s
Liquid Apogee Motor (LAM) in six steps, the apogee of the orbit will be
raised further and further. Ultimately, the spacecraft will be put on a course
for arriving at Mars in September 2014. In this fuel efficient ‘Mars Transfer
Trajectory’, the spacecraft travels for about 300 days under the influence of
the Sun and approaches Mars.

At that time, the spacecraft’s speed is reduced by suitably firing its LAM to
enable it to be captured into an orbit by Martian gravity. After achieving this
elliptical orbit around Mars with a periareion (nearest point to Mars) of
366 km and an apoareion (farthest point to Mars) of 80,000 km, the
spacecraft is scheduled to begin its six month observation of that planet and
its atmosphere.

The Spacecraft
The 1340 kg Mars Orbiter spacecraft is based on the modified version of
ISRO’s well proven one ton class platform (I1K satellite bus). The
spacecraft structure is built mainly by the use of lightweight Aluminium alloy
and composites like Carbon Fibre Reinforced Plastic (CFRP). To keep the
spacecraft within safe temperature limits, a variety of materials including
Multilayer Insulation (MLI) blanket are used. The Mechanisms subsystem of
the spacecraft facilitates the deployment of the spacecraft’s solar panels
and the high gain antenna, as well as the rotation of the solar array drive to
track the sun and generate optimum electric power.
The spacecraft’s single solar array consisting of three panels can generate
about 840 W of electric power in the Martian orbit. A 36 Ampere-Hour
Lithium-Ion battery supplies power to the spacecraft during eclipse and peak
power requirement periods. The transmission of spacecraft health related
information to Earth, enabling the knowledge of its position in space, and the
reception of telecommands from Earth are performed by the Telemetry,
Tracking and Command (TTC) subsystem of the spacecraft working in
S-band.
The images and other science data gathered by the spacecraft’s five
payloads are transmitted to Earth by its 2.2 m dish shaped S-band high gain
antenna.

Mars Orbiter spacecraft carries a host of Sun and Star Sensors as well as
an Inertial Reference Unit and accelerometers that provide information on
the spacecraft’s precise orientation and velocity. The microprocessor based
Attitude and Orbit Control Electronics (AOCE) of the spacecraft maintains
and controls the orientation and orbit of the spacecraft using its reaction
wheels, thrusters and the Liquid Apogee Motor (LAM). About 850 kg of
propellants required for LAM and thrusters are stored in the spacecraft’s
tanks.

The Payloads
Mars Orbiter Mission carries five scientific payloads to observe Martian
surface, atmosphere and exosphere extending up to 80,000 km for a
detailed understanding of the evolution of that planet, especially the related
geologic and the possible biogenic processes on that interesting planet.
These payloads consist of a camera, two spectrometers, a radiometer and a
photometer. Together, they have a weight of about 15 kg.

Mars Colour Camera (MCC) is a versatile and multi-purpose snap shot
CCD camera to map various morphological features on the Martian surface
and return colour visual images of Mars and its environs. MCC is expected
to observe and help us understand events like dust storms, dust devils, etc.,
that are known to occur on Mars. MCC will have a resolution of
19.5 m when it is at nearest point to Mars in its elliptical orbit (periareion)
and will be capable of imaging the full disc of Mars starting from 63,000 km
and extending upto the farthest point (apoaerion). Besides, there can be a
few opportunity based objectives like imaging one of the moons of
Mars – Phobos – and other celestial objects like comets or asteroids,
if appropriately illuminated.

Thermal Infra-Red Imaging Spectrometer (TIS) is a grating based
spectrometer that will measure the thermal emission from Martian surface.
The data acquired will be useful for mapping the temperature of the Martian
surface and to study the composition and mineralogy of Mars. TIS operates
in the Thermal Infrared (TIR) region (7 micron to 13 micron) and has a
resolution of 258 m at periareion (around 366 km) and 55 km at apoareion
(around 80,000 km).

Methane Sensor for Mars (MSM) is a differential radiometer operating in
the Short Wave Infrared (SWIR) region. It measures solar radiance in two
SWIR channels. MSM can measure Methane concentration in the Martian
atmosphere accurately. Variation of methane over different places and at
different times derived from MSM data may provide some insight regarding
its origin as to whether it is biological or geological.

Mars Exospheric Neutral Composition Analyser (MENCA) is a
quadrupole mass spectrometer based scientific payload. MENCA will be
capable of measuring relative abundances of neutral constituents in the
mass range of 1 to 300 atomic mass units (amu), with a unit mass
resolution. It will study the neutral composition and density distribution of
the Martian exosphere from about 370 km altitude and beyond. This would
help in understanding the escape of the Martian atmosphere.

Lyman Alpha Photometer (LAP) is a far-ultraviolet (FUV) scientific
  instrument. LAP is primarily dedicated to measure the relative abundance of
  Deuterium and Hydrogen from their Lyman-alpha emissions in the Martian
  exosphere. Currently, it is aimed at the in-situ estimation of deuterium
  enrichment and to further the understanding of loss process of water from
  Martian atmosphere.

                                                                                     Power
                  Primary        Developed     Operating                                     Weight
  Payload                                                         Resolution        Require
                  Objective         by          range                                         (Kg)
                                                                                    ment (W)

Mars Colour  Optical imaging                  0.4 – 0.7 µm                             3        1.27
                                   SAC                        19.5 m @ periareion
Camera (MCC)                                     R-G-B
Thermal Infra- Map surface                                      258 m (~366km)

The Ground Segment
The Ground Segment of Mars Orbiter Mission mainly consists of facilities to
monitor the spacecraft and its flight status during various phases of
mission, and to control them. Indian Space Science Data Centre, which
processes and archives data from the spacecraft, also forms an important
part of the ground segment.

Besides the ground stations of ISRO Telemetry, Tracking and Command
Network (ISTRAC) in India and abroad, two shipborne S-band terminals will
be used to monitor the performance and flight of PSLV-C25 vehicle and
Mars Orbiter Mission spacecraft over the Pacific.

During the earth orbiting phase of the spacecraft, ISTRAC network of
ground stations will be used. Once the spacecraft enters deep space
(beyond 100,000 from the Earth), 18 and 32 metre antennas of Indian Deep
Space Network (IDSN) at Byalalu near Bangalore and antennas of NASA’s
Deep Space Network will be utilised to communicate with the spacecraft as
well as to track and control it. These two networks continue their support till
the mission completion.

The Spacecraft Control Centre at Bangalore acts as the nerve centre of
mission operations during various phases of the mission.

Publication and Public Relations Unit, ISRO                   November 2, 2013